The invention relates to an image scanning and recording method which utilizes such a scanner as is used for the photomechanics or the plate making process. More particularly, it relates to a method for recording an original picture wherein digital signals derived from a pictorial figure of a continuous tone are combined with other digital signals derived from a line drawing or letters of binary levels such as black and white.
Picture scanning and recording apparatus should have in general some kinds of editing functions. For example, a plurality of original pictures are to be recorded on a single photosensitive material according to a predetermined layout. Further in the other cases, a continuously gradated picture and letters or line drawings of binary tones such as black and white have to be synthesized giving a duplicate edited also in accordance with a predetermined layout. Such letters or drawings consist of fine thin lines which produce binary signals when scanned so that a higher resolving power is needed in scanning them than in scanning the pictures of continuous gradation. In the event that the higher power were also applied to said pictures, the overall processing time would be exceedingly prolonged resulting in a serious disadvantage for such a system.
Furthermore, such an excessive resolving power would need of course a higher memory capacity of magnetic discs which are usually utilized for layout operation of data obtained by scanning the picture and letters. This excessive memory capacity will also inevitably prolong the overall processing time.
I have previously proposed a new method for writing into a memory disc a set of picture signals together with a set of line drawings signals. Both the sets of signals have been subjected to a layout operation prior to the writing step, and are stored in the memory disc in such a manner that they can be separated from one another. Said signals are then sequentially read out of the memory disc to thereby produce duplicates in which the image of an original picture coexists with those of the line drawings.
It is, however, to be noted that this previously proposed method has a certain disadvantage despite its various merits. Namely, either a portion of said picture or that of said line drawings is exclusively recorded for each fine element of the picture so that a blank unprinted area is likely to appear along the contour lines of said line drawings duplicated in the abovesaid manner.
FIG. 1 illustrates an example of half-tone image having a blank area.
The references (P.sub.1) and (P.sub.2) in FIG. 1 respectively indicate a pitch of pictorial elements of the picture and that of the line drawing. A portion (A) of the picture comprises a plurality of dots (A') whose size is in accordance with a density of said portion. A references (C) indicate a blank unprinted area formed along the contour line of a line drawing portion (B).